41 results about "Magnetization curve" patented technology

The present invention relates to the technical field of motor design, and provides a method for calculating a leakage magnetic coefficient of a closed slot in a rotor of an asynchronous motor. According to the calculation method provided by the present invention, by means of diverting the magnetic flux of rotor teeth in combination with a relative magnetic permeability calculated from a magnetization curve, a closed slot is ultimately transformed equivalently into a semi-closed slot, thereby unifying the semi-closed-slot and closed-slot algorithms and improving the adaptability of the closed-slot algorithm. The present method provides a general algorithm for closed-slot parameters, takes into account the edge effects caused by punching and shearing of cold-rolled silicon steel sheets, and is applicable to closed slots of various rotor slot types. Compared to finite-element methods, the present method has a short calculation cycle and is suitable for programmatic processing.

The invention discloses a high-power inverter and a control method thereof, and belongs to the technical field of power electronics, the high-power inverter comprises a sensing enhanced magnetic assembly, the sensing enhanced magnetic assembly comprises a high-thermal-conductivity metal shell, a magnetic core arranged in the high-thermal-conductivity metal shell, a main power coil, a high-precision sensing coil and an integrated thermal probe; wherein the high-precision sensing coil is wound by clinging to a central column of the magnetic core, the main power coil is coaxially wound on the outer side of the high-precision sensing coil, and the magnetic core, the main power coil and the high-precision sensing coil jointly form an inductor core body. According to the invention, the controller can monitor the working point of the magnetic core on the magnetization curve in real time, so that the margin of the magnetic core away from the magnetic saturation state is directly judged.

The invention discloses a nonlinear permanent magnet hysteresis loop description method based on magnetic domain energy minimization. The method comprises the following steps: step 1, forming a state equation by using total energy obtained by adding magnetic domain energy of six magnetic domains along easy axis directions of different crystals in permanent magnet crystal grains; 2, the minimum value of magnetic domain energy is solved, and then the optimal direction of each magnetic domain unit magnetization vector in the crystal grains is obtained; and step 3, describing a magnetic domain occurrence probability by using a Boltzmann function, and determining a Preisach model distribution function by using a probability density function so as to obtain a macroscopic hysteresis characteristic. According to the method, micro-magnetic microcosmic characterization and macroscopic magnetic performance are associated from a micromechanism, a magnetization curve of a nonlinear permanent magnet can be accurately established, and the method has an important supporting effect on research work such as electromagnetic multi-physics field simulation and the like.

The invention discloses an analytical calculation method suitable for the magnetic saturation current of a high-voltage shunt reactor under a resonance working condition. The method comprises the following steps: establishing an electromagnetic coupling equivalent circuit model under the resonance working condition of the shunt reactor considering the magnetic saturation characteristic of an iron core; dividing the magnetization characteristic of the iron core into an unsaturated section and a saturated section through piecewise linearization processing of the magnetization curves, and setting the slopes of the two sections of magnetization curves and the magnetic field intensity at the knee point of a demarcation point; according to the working state of the reactor, constructing an electromagnetic coupling equation set containing a first-order conducting term coefficient in an unsaturated state, and deducing a time domain analytical expression of winding current; constructing an electromagnetic coupling equation set considering a zero-sequence coupling effect in a saturated state, simplifying resistance parameters, and then deducing a current solution expression in an equivalent inductance matrix form; the current value of the three-phase winding of the shunt reactor is monitored in real time, when the current amplitude of the winding reaches a knee point value, state switching is triggered, the final value of the previous state is used for updating the initial condition of the next state, and the current waveform is solved.

The present invention relates to the field of deformation monitoring, and particularly to a method and system for monitoring the deformation of magnetic materials. The method first obtains the magnetization curves and deformation amounts of each magnetic material in the same production batch, and uniformly selects a plurality of positions to be measured on the horizontal axis of the coordinate system. According to the distribution of the magnetic induction intensity and the distribution of the deformation amount at the target positions to be measured of the reference magnetic material of the target magnetic material, the deformation evaluation ability of the magnetization curve of the target magnetic material at the target positions to be measured is obtained. Furthermore, the importance of each position to be measured is analyzed, and key positions to be measured are screened out from all the positions to be measured. Based on the magnetic field intensity and magnetic induction intensity of the magnetization curves of each magnetic material at the key positions to be measured, and the deformation amounts of each magnetic material, a deformation monitoring model is constructed, and the deformation monitoring model is used to monitor the deformation of the magnetic materials to be monitored. The present invention can improve the accuracy of monitoring the deformation of magnetic materials.

The application provides a Fe3O4 nanoparticle microscopic imaging detection method based on left and right polarization modulation, belongs to the technical field of photothermal science and detection and signal processing, and solves the problems that current nanometer single particles are difficult to observe and physical and chemical characteristics are difficult to obtain, and specifically comprises the following steps: determining a sample to be detected and preparing a slide sample; starting a computer, a data acquisition card, a lock-in amplifier, a galvanometer controller and a function generator; starting a power supply of an excitation light and a detection light laser and a refrigerator; setting detection parameters, setting laser power / current parameters, setting modulation parameters, and scanning and detecting the sample to be detected; loading a magnetic field; reading signals from the data acquisition card by the computer to obtain a photothermal detection result image; changing different laser parameters and the size of the magnetic field, repeating the above steps, obtaining a circular dichroism and magnetic circular dichroism detection result, measuring a magnetization curve, and monitoring a single nanoparticle magnetic moment flipping process.

This invention relates to a testing device for the magnetic properties of high-permeability materials under low-frequency weak magnetic environments, comprising: a coil assembly, a magnetic property tester, a magnetic shielding cylinder, and a host computer; the coil assembly is wound around the sample under test and connected to the magnetic property tester, and the sample under test with the coil assembly placed inside the magnetic shielding cylinder; the magnetic shielding cylinder provides a weak magnetic environment for the sample under test; the magnetic property tester is used to provide excitation current to the coil assembly and detect the induced voltage of the sample under test, and transmit the measured data to the host computer; the host computer is used to acquire the data measured by the magnetic property tester and plot the magnetization curve. The technical solution of this invention solves the problem that current magnetic property testing devices for magnetic materials cannot obtain the permeability of high-permeability materials under low-frequency weak magnetic environments, thereby improving the accuracy and precision of theoretical and simulation calculations of magnetic shielding devices and reducing the error between design and actual values.

The invention relates to the technical field of power transformer state monitoring, and discloses a transformer direct current magnetic bias current measuring method. According to the method, an initial characteristic model containing a magnetization curve inflection point and a winding resistance temperature coefficient is constructed based on a nameplate and historical data; when a transformer is in grid-connected operation, an exciting current transient waveform and a neutral point potential fluctuation sequence are synchronously captured, a direct current magnetic bias characteristic distortion component is separated from exciting current by using a model, and a neutral point potential trend term is decomposed to extract a direct current voltage residual error. And establishing a dynamic mapping relation between the two, and generating a direct current injection analog signal to be applied to the equivalent simulation loop. By calibrating the signal amplitude, the simulation and actual measurement exciting current characteristics reach a preset similarity, and finally, the calibrated steady-state amplitude is reversely converted into a primary side direct current magnetic bias current value. According to the method, the difficulty of direct measurement is avoided, and high-precision equivalent measurement of the direct-current magnetic bias current is realized through model analysis and simulation calibration.

The application discloses a kind of magnetic nanoparticle magnetization response and frequency spectrum measuring device and method under multi-frequency magnetic field excitation, belong to nanometer test technical field, comprising: setting excitation magnetic field frequency and amplitude, generating alternating excitation magnetic field;The magnetization response of the measured magnetic nanoparticle sample under alternating magnetic field excitation is measured, and the magnetization response spectrum information thereof is obtained;The detection characteristics of the measured magnetic nanoparticle sample are calculated using the amplitude and phase of each harmonic of the magnetization response spectrum, and the dynamic magnetization curve of the measured magnetic nanoparticle sample is reconstructed.The application can realize the measurement of the magnetization response, spectrum and magnetization curve of the magnetic nanoparticle sample under multi-frequency magnetic field excitation, and can be applied to the calibration and measurement of the concentration of the magnetic nanoparticle under multi-frequency magnetic field excitation.

This application provides a modeling method and system for predicting the core loss of a high-frequency transformer, comprising: measuring the magnetic properties of the core material at different frequencies based on an experimental platform, and obtaining the magnetization curve and loss density curve of the core material according to Ampere's circuital law; inputting the magnetization curve into a constructed geometric model, setting excitation and boundary conditions, establishing a finite element model and performing finite element simulation analysis to obtain the loss density distribution and magnetic flux density distribution within the high-frequency transformer core; and constructing a loss model by introducing a gradient coefficient and the average value of the loss density, the magnitude of the magnetic field strength gradient, and the average value of the magnitude of the magnetic field strength gradient obtained from the finite element model, to predict the core loss. This application provides important basis for material selection, geometric structure optimization, and thermal design of high-frequency transformers, helping to shorten the R&D cycle, reduce trial production costs, and improve the overall performance of high-frequency transformers.

This disclosure relates to the field of magnetic shielding technology, and proposes a method, apparatus, electronic device, and readable storage medium for detecting the residual magnetism state. The method includes: acquiring a calibration magnetization curve, which is generated based on recorded response data of the target magnetic shielding layer to a calibration excitation pulse, and includes the correlation between surface residual magnetism change curves, voltage change curves, and current change curves; transmitting a test excitation pulse to the target magnetic shielding layer to acquire test voltage data and test current data; wherein the test pulse width of the test excitation pulse is less than a preset proportion of the calibration pulse width of the calibration excitation pulse; and comparing the test voltage data and test current data with the calibration magnetization curve to determine the current residual magnetism state of the target magnetic shielding layer. The technical solutions provided by one or more embodiments of this disclosure can effectively detect the residual magnetism state of the magnetic shielding layer in a magnetic shielding device.

Control of magnet ramp profiles with predetermined ramp rates in Czochralski silicon crystal growth to mitigate the transient behavior in silicon melt flow and its impact to semiconductor silicon crystal growth and crystal quality. The magnetic field strength may be regulated in at least two stages or at least three stages of growth of the constant diameter portion of the ingot.

The invention provides a three-dimensional rotating magnetic measurement device and a three-dimensional rotating magnetic measurement system, and relates to the technical field of magnetic measurement. The three-dimensional rotation magnetic measurement device comprises a base, a first rotation driving assembly, a second rotation driving assembly and a supporting rod, the first rotation driving assembly, the second rotation driving assembly and the supporting rod are arranged on the base, a sample base is arranged in the supporting rod and used for fixing a sample to be measured, and the sample base is in driving connection with the output end of the first rotation driving assembly. The supporting rod is in driving connection with the output end of the first rotating driving assembly to rotate around the first axis under driving of the first rotating driving assembly, the supporting rod is in driving connection with the output end of the second rotating driving assembly to rotate around the second axis under driving of the second rotating driving assembly, and the second axis is perpendicular to the first axis. The three-dimensional rotation magnetic measurement device can obtain the three-dimensional anisotropy information of the sample to be measured, is high in measurement efficiency and data reliability, and can construct a complete three-dimensional magnetization curved surface / ellipsoid.

The present invention relates to the field of filter element detection technology, and in particular to a silver-based composite filter element detection method and system. The present invention draws a magnetization curve according to an initial magnetic induction intensity value, a plurality of first magnetic induction intensity values, and a second magnetic induction intensity value. By analyzing the magnetization curve, the magnetic response data of the silver-based fiber under different external magnetic field intensities can be quickly obtained. The external magnetic permeability of the silver-based fiber is calculated according to the plurality of second magnetic induction intensity values ​​and the first magnetic induction intensity value. Compared with traditional chemical analysis methods such as atomic absorption spectroscopy, the calculation of the external magnetic permeability can usually be completed more quickly, making the evaluation of the silver content of the silver-based fiber more accurate. The magnetic susceptibility of the silver-based fiber is obtained according to the magnetization curve. The relative amount of the silver content can be indirectly inferred by calculating the magnetic susceptibility. The silver content is calculated according to the magnetic susceptibility, the external magnetic permeability, the residual magnetization intensity, and the plurality of saturation magnetization intensities, so that the silver content can be calculated in more detail and accurately.

The invention belongs to the technical field of measuring equipment, and particularly relates to a motor detection system and method for harbor machinery, and the system comprises a controller, a magnetic core, a magnetic field detection unit, and a bias magnetic field output unit. When the magnetic core is sleeved on the detected lead, the controller is configured to detect a magnetic field intensity change curve through the magnetic field detection unit; when the magnetic field intensity change curve is abnormal, the controller is further configured to drive the bias magnetic field output unit to output a corresponding bias magnetic field so as to adjust the magnetic field intensity change curve; the bias magnetic field output unit is arranged on the outer side of the magnetic core, so that the influence of an external magnetic field on the magnetic core magnetic conductivity can be restrained, namely the bias magnetic field is generated through the bias magnetic field output unit, a magnetic core working point is stabilized in a magnetization curve linear region, and therefore the influence of the external magnetic field on the magnetic core magnetic conductivity is eliminated; the magnetic field intensity change curve is accurately measured so as to truly reflect the insulation performance of the motor.

This invention discloses a high-power inverter and its control method, belonging to the field of power electronics technology. It includes a sensing-enhanced magnetic component, comprising a high thermal conductivity metal casing, a magnetic core disposed inside the high thermal conductivity metal casing, a main power coil, a high-precision sensing coil, and an integrated thermal probe. The high-precision sensing coil is wound close to the central post of the magnetic core, and the main power coil is coaxially wound around the outside of the high-precision sensing coil. The magnetic core, the main power coil, and the high-precision sensing coil together constitute the inductor core. This invention enables the controller to monitor the operating point of the magnetic core on the magnetization curve in real time, thereby directly determining its margin from magnetic saturation.

The invention discloses a manufacturing method of a magnetic response millimeter-scale adhesion mobile robot for intragastric targeted drug delivery and pathological detection and the adhesion mobile robot. The method comprises the following steps: manufacturing a magnetic sheet with a simple harmonic magnetization curve; manufacturing a flexible frame, wherein a plurality of mounting holes for accommodating magnetic sheets are formed in the flexible frame; each magnetic sheet with a simple harmonic magnetization curve is mounted to a flexible frame, thereby forming a magnetic response millimeter-scale adhesion mobile robot for intragastric targeted drug delivery and pathological detection. According to the adhesion mobile robot manufactured through the method, the thin liquid film is transmitted on the wet and slippery surface through wave type movement of the magnetic response sheet-shaped soft material, so that crawling propelling is achieved by means of counter-acting force generated by the liquid film, the robot can stably crawl on the wet and low-friction stomach tissue surface by means of the adhesion moving characteristic, and the robot has a good application prospect. Good environmental adaptability is shown.

This invention relates to the field of soft magnetic materials technology, and in particular to a Fe-Co-Al soft magnetic material, its preparation method, and its applications. The material is prepared from Fe, Co, and Al as raw materials, weighed according to an atomic ratio of Fe:Co:Al = 3:1:1, and then processed through melting, rapid cooling, and heat treatment to obtain a soft magnetic material with the chemical formula Fe₃CoAl. The resulting material has a fully ordered cubic crystal structure of type DO₃. At room temperature, it exhibits a saturation magnetization of 162 emu / g, a coercivity of approximately 28.5 Oe, and a steep initial magnetization curve, demonstrating excellent magnetization sensitivity and rapid response even under weak magnetic fields. The Fe₃CoAl soft magnetic material of this invention significantly improves permeability and reduces coercivity through the introduction of Co, and its preparation process is simple, has a short cycle time, and is suitable for industrial production.

The present invention provides a tunneling magnetoresistance and a manufacturing method thereof. The tunneling magnetoresistance includes: a first pinned layer; a free layer disposed opposite to the first pinned layer; a tunneling barrier layer located between the first pinned layer and the free layer; and a second pinned layer located on a side of the free layer facing away from the tunneling barrier layer. The second pinned layer can provide a weak exchange bias field for the free layer. After the external environmental temperature or the external magnetic field is removed, the exchange bias field can pin the direction of the free layer in the initial state, thereby avoiding the problem that the initial state of the vortex magnetization of the tunneling magnetoresistance is unstable and is easily affected by changes in the external environment, resulting in the drift of the magnetization curve. It has the effect of stabilizing the free layer and increasing the temperature stability of the free layer.

The invention relates to the technical field of motors, in particular to a motor stator core electromagnetic characteristic measuring device and a motor simulation model calibration method, and the device comprises a stator support, a stator core, a rotor core, a rotating shaft, a shaft support, an excitation winding, an induction coil and an H coil. An exciting winding is wound in a rotor slot, alternating current is introduced into the winding to form a rotating magnetic field, an induction coil is wound on a stator tooth part to measure the magnetic induction intensity of the stator tooth part, an H coil is tightly attached to the surface of the stator tooth part to measure the magnetic field intensity of the stator tooth part, and the iron loss of the motor can be obtained by using input power and winding copper loss. And the stator loss is obtained by using the iron loss proportional relation in the finite element. And inputting the measured stator magnetization curve and loss curve into a finite element for correcting a finite element model. According to the method, through accurate magnetic field solution, loss analysis and model calibration, the simulation precision of the motor electromagnetic simulation model is effectively improved.

The invention discloses an experimental method for separating stator slotted core tooth part yoke part magnetization and loss, which comprises the following steps of: firstly, winding a primary / secondary side winding on a stator yoke part, testing to obtain the loss and magnetization curve of the yoke part according to the basic principle of a transformer, and then stacking two same stator teeth in a tooth-to-tooth manner to obtain the loss and magnetization curve of the yoke part. Primary / secondary side coils are placed at the same position teeth of an upper stator and a lower stator, a magnetization and loss curve of a tooth part is obtained through testing, the magnetization and loss curve of a yoke part and the magnetization curve of the tooth part are input into a finite element, magnetic pressure drop and loss of the yoke part are solved, yoke part related data are removed from the experiment data of the magnetization and loss curve of the tooth part, and the magnetic pressure drop and loss of the yoke part are calculated. According to the stator slotted core tooth part / yoke part magnetization and loss separation experiment method provided by the invention, the magnetization and loss curve of the tooth part can be directly measured, and the deterioration influence of slotting on the tooth part can be quantitatively analyzed.

The invention relates to the technical field of magnetic shielding, and provides a residual magnetism state detection method and device, electronic equipment and a readable storage medium, and the method comprises the steps: obtaining a calibration magnetization curve, and enabling the calibration magnetization curve to be generated according to the response record data of a target magnetic shielding layer to a calibration excitation pulse, the calibration magnetization curve comprises a correlation corresponding relation among a surface residual magnetism change curve, a voltage change curve and a current change curve; aiming at the target magnetic shielding layer, transmitting a test excitation pulse, and obtaining test voltage data and test current data; wherein the test pulse width of the test excitation pulse is smaller than the preset proportion of the calibration pulse width of the calibration excitation pulse; and comparing the test voltage data and the test current data with the calibration magnetization curve to determine the current residual magnetism state of the target magnetic shielding layer. According to the technical scheme provided by one or more embodiments, the residual magnetism state of the magnetic shielding layer in the magnetic shielding device can be effectively detected.

The invention relates to an MRAM (Magnetic Random Access Memory) detection method based on a magnetic field injection and optical detection coupling technology. The method comprises the following steps: loading a to-be-detected MRAM sample to the center of a magnet coil wound by a magnetic domain; the current in the magnet coil is controlled, and the required magnetic field intensity and direction are loaded; observing the magnetic domain structure and the magnetization behavior of the MRAM sample by using an MOKE microscope, and recording the polarization change of the reflected light; measuring magnetization curves of the MRAM sample in different magnetic fields by using a VSM to obtain magnetic parameters; observing the morphology and magnetic characteristics of the surface of the MRAM sample by using an AFM, and detecting the magnetic force change in a magnetic force detection mode; observing a microstructure and a magnetic domain structure of the MRAM sample by using a TEM (Transmission Electron Microscope); and observing the magnetic domain structure and the magnetic characteristics of the surface of the MRAM sample by using the MFM.

The present invention discloses a method for simulating the hysteresis characteristics of soft magnetic materials based on an analytical inverse Preisach model, comprising: first, based on the analytical positive Preisach model, using the derivation rule to derive analytical expressions for the initial magnetization curve, the ascending branch of the limiting hysteresis loop, and the descending branch of the magnetic permeability, respectively; then, based on the difference method, deriving analytical expressions for the initial magnetization curve, the ascending branch of the limiting hysteresis loop, and the descending branch of the magnetic permeability, respectively, with the current magnetic induction intensity as input and the current magnetic field intensity as output, thereby obtaining an analytical inverse Preisach model. The analytical inverse Preisach model parameters are then extracted based on a genetic algorithm and three measured hysteresis loops under high, medium, and low magnetic densities, and the hysteresis loops of the soft magnetic material under different working conditions are calculated based on the model and parameters. The analytical inverse Preisach model proposed in the present invention can not only accurately and quickly simulate the hysteresis characteristics of soft magnetic materials, but also plays an important supporting role in research work such as core loss calculation, electromagnetic multi-physics field simulation, and global structural optimization design of electrical equipment.

This invention discloses a current inversion method for steel-tape armored multi-core cables, comprising: S1, setting multiple measurement points at the test location of the multi-core cable, establishing a polar coordinate system with the geometric center of the cable as the origin, and constructing a position coefficient matrix, a conductor current matrix, and an attenuation coefficient matrix; S2, assigning initial values ​​to the unknown variables, and calculating the initial conductor current matrix and the initial attenuation coefficient matrix; S3, finding the local optimum solution of the attenuation coefficient matrix using a stochastic optimization method; S4, constructing a system of linear equations with the conductor current matrix as the unknown variable to solve for the conductor current matrix; S5, after updating the sampled values ​​of the magnetic induction intensity components, solving the system of linear equations to calculate the current values ​​of each conductor in the cable. Based on the time-invariant properties of the magnetization curve, this invention utilizes a stochastic optimization algorithm to solve for the undetermined coefficients of the approximation function, solves for the nonlinear attenuation coefficient of the steel-tape armor of the target cable, corrects the influence of the steel-tape armor on the current inversion results, and improves measurement efficiency and accuracy.

The invention relates to a field-circuit coupling simulation method and system of a transformer, computer equipment and a medium. According to the field-circuit coupling simulation method of the transformer, the magnetization curve of the to-be-tested transformer is fitted through a high-order interpolation method, so that the stability and the precision when a nonlinear finite element equation of an electromagnetic field of the transformer is solved are effectively improved, the stability of field-circuit coupling simulation of the transformer is ensured, the numerical oscillation phenomenon generated by field-circuit coupling simulation of the transformer is avoided, and the reliability of field-circuit coupling simulation of the transformer is improved. According to the method, the operation efficiency and reliability of transformer field-circuit coupling simulation can be improved, meanwhile, the calculation amount of nonlinear equation solving is effectively reduced, the solving efficiency is improved, and the efficiency of transformer field-circuit coupling simulation can be improved.

The invention discloses a ferromagnetic material Isin model parameter inversion method and system based on hysteresis characteristics, and the method comprises the steps: obtaining an initial magnetization curve and a saturation hysteresis loop of a ferromagnetic material, and determining an experiment excitation magnetic field sequence; constructing a three-dimensional Isin model; inputting an excitation magnetic field sequence, calculating and generating a simulated initial magnetization curve and a saturated hysteresis loop by using a three-dimensional Isin model, and constructing a training data set containing a large number of sample pairs; constructing a parameter inversion neural network model, and performing supervised learning training on the neural network model by using the training data set; and inputting the experimental hysteresis characteristics into the trained parameter inversion neural network model, and outputting an optimal model parameter combination matched with the experimental hysteresis characteristics of the ferromagnetic material. According to the method, physical constraint is carried out on the Isin model by utilizing the hysteresis characteristic of a macroscopic experiment, inversion of relevant parameters of a microscopic magnetic domain structure in the model is realized, and a modeling basis is provided for further carrying out magnetic Barkhausen noise signal simulation and magnetic characteristic prediction.

The application discloses a hysteresis loop fitting method, and relates to the technical field of hysteresis loop fitting, and comprises the following steps: using an alternating gradient magnetic measurement device, sequentially performing sweep frequency testing and sweep field testing on a test sample, and obtaining a raw data pair of the vibration speed and the magnetic field intensity of the test sample; preprocessing the magnetic field intensity signal of the test sample, and piecewise fitting magnetization curves and demagnetization curves; using a complex nonlinear function comprising a polynomial function term and an exponential function term to fit the hysteresis loop of the test sample; solving the related parameters of the complex nonlinear function; and establishing the fitted hysteresis loop of the vibration speed and the magnetic field intensity of the test sample according to the solved related parameters. The application can ensure the accuracy of the fitted hysteresis loop result, has sufficient model convergence speed, and has good noise resistance effect.

A method for determining characteristics of a laminated core transformer and related device, the magnetic characteristics and / or loss characteristics of the laminated core transformer are determined based on an equivalent magnetic circuit model and magnetic induction under a direct current biasing condition. The equivalent magnetic circuit model is generated by equivalent correction of magnetic circuit parameters based on a direct current magnetic potential generated by a direct current component of a winding current when the laminated core transformer is in operation, the magnetic circuit parameters corresponding to an alternating current equivalent magnetic circuit model of a joint area of the laminated core transformer under a condition of no direct current biasing, the alternating current equivalent magnetic circuit model being generated based on a two-dimensional equivalent planar structure of the joint area, a magnetization curve and a core loss curve of a silicon steel sheet material. The equivalent magnetic circuit model can reflect a physical process in which the joint area preferentially enters a nonlinear magnetization region and a magnetic flux path is reconstructed under the action of the direct current biasing. Based on the equivalent magnetic circuit model, the influence of the direct current biasing on the magnetic characteristics and core loss of the laminated core transformer as a whole can be effectively reduced or avoided.

The application discloses an imaging method based on magnetization curve fitting of magnetic particle relaxation time, comprising: generating a magnetic field free point (FFP); moving the FFP in a space range where a single magnetic nanoparticle-injected target object is located, generating a pulsed square wave excitation magnetic field at each FFP position, and receiving original signals generated by magnetic nanoparticles in the target object under excitation of the pulsed square wave excitation magnetic field; fitting a target magnetization curve by adjusting relaxation time related parameters in a preset double exponential decay function based on the original signals; taking an adjustment result of the corresponding relaxation time related parameters as a magnetic particle relaxation time detection result of the FFP position; and performing imaging based on at least one same item in the magnetic particle relaxation time detection results obtained based on all FFP positions to obtain a relaxation time imaging graph. The application can separately detect the relaxation time, and combines the FFP scanning to perform multi-color magnetic particle imaging to distinguish plaque, duct and blood vessel regions.